Axle driving apparatus for a zero turn radius vehicle

ABSTRACT

An axle driving apparatus includes a first housing having a plurality of cooling fins, an axle rotatably mounted in the first housing, a hydraulic stepless speed change assembly disposed within the first housing. The axle driving apparatus also includes a second housing having a plurality of cooling fins, an axle rotatably mounted in the second housing, a hydraulic stepless speed change assembly disposed within the second housing. A connecting means, such as a bar and/or plate connects the first and second housings. The plurality of cooling fins on the first housing has a different configuration that the plurality of cooling fins on the second housing.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to an axle driving apparatus designed to drive azero turn radius vehicle.

Background Art

An axle driving apparatus having a hydrostatic transmission (HSTs) isgenerally known in the art. An HST includes a center section on which ismounted a hydraulic pump and a hydraulic motor. The hydraulic pump andthe hydraulic motor each carry a plurality of reciprocating pistons thatare in fluid communication through porting formed in the center section.As the hydraulic pump rotates, the pump pistons move axially as theybear against an adjustable swash plate where the degree of axialmovement depends upon the angular orientation of the swash plate. Axialmovement of the pump pistons forces the hydraulic fluid through theporting, which forces the motor pistons against a thrust bearing tothereby rotate the hydraulic motor. As the hydraulic motor rotates,hydraulic fluid is returned to the hydraulic pump through the porting.In this manner, the rotation of the hydraulic pump is translated to thehydraulic motor and the rotation of the hydraulic motor may be used todrive an axle or a pair of axles through a differential. In the case ofa transaxle, both left and right wheels are driven together so the speedcannot be independently controlled. This results in a larger turningradius, making it difficult to make close turns. When used in lawn orgarden tractors, it is difficult to move close to trees or otherobstacles.

Alternatively, there can be one HST for each wheel so that each wheelcan be driven independently. Such zero turn HSTs provide for independentcontrol of each of the drive wheels. Improvements and modifications arefrequently being made to HSTs with a zero turn radius.

BRIEF SUMMARY OF THE INVENTION

Disclosed herein is an axle driving apparatus of a first embodiment thatincludes a first housing having a first plurality of cooling fins; afirst axle, having a first longitudinal axis, rotatably mounted in thefirst housing; a first hydraulic stepless speed change assembly disposedwithin the first housing, the first hydraulic stepless speed changeassembly including a first hydraulic pump having a first input shaft,said first input shaft having a rotational axis substantiallyperpendicular to said first axle, and including a first hydraulic motorhaving a first output shaft drivingly connected to said first axle; asecond housing having a second plurality of cooling fins; a second axle,having a second longitudinal axis, rotatably mounted in the secondhousing; a second hydraulic stepless speed change assembly disposedwithin the second housing, the second hydraulic stepless speed changeassembly including a second hydraulic pump having a second input shaft,said second input shaft having a rotational axis substantiallyperpendicular to said second axle, and including a second hydraulicmotor having a second output shaft drivingly connected to said secondaxle; and a connecting means connecting the first and second housings.The first plurality of cooling fins and the second plurality of coolingfins have different configurations.

Further, the first plurality of cooling fins may be bent at an angledifferent from an angle at which the second plurality of cooling finsare bent.

The axle driving apparatus may also include a first hydraulic PTO unithaving a first charge pump, wherein the first hydraulic PTO unit isconnected to a first plurality of auxiliary ports in the first housing.

Further, the second housing may have a second plurality of auxiliaryports.

The axle driving apparatus may also include a second hydraulic PTO unithaving a second charge pump, wherein the second hydraulic PTO unit isconnected to the second plurality of auxiliary ports.

Further, the second plurality of auxiliary ports may be closed off.

The axle driving apparatus may also include a first input pulleydisposed on the first input shaft and a second input pulley disposed onthe second input shaft.

The axle driving apparatus may also include a first spline collarsurrounding the first input shaft; a first bearing support surroundingthe first spline collar; a second spline collar surrounding the secondinput shaft; and a second bearing support surrounding the second splinecollar. The first input pulley may be disposed on the first bearingsupport and the second input pulley may be disposed on the secondbearing support.

The axle driving apparatus may also include a first input pulley; afirst cooling fan mounted on the first input shaft; a first wave washerlocated between the first input pulley and the first cooling fan; asecond input pulley; a second cooling fan mounted on the second inputshaft; and a second wave washer located between the second input pulleyand the second cooling fan.

The axle driving apparatus may also include a first oil sump formed inthe first housing, wherein the first hydraulic stepless speed changeassembly is at least partially immersed in the first oil sump; a firstreserve tank; a first siphon allowing flow in both directions betweenthe first oil sump and the first reserve tank; a second oil sump formedin the second housing, wherein the second hydraulic stepless speedchange assembly is at least partially immersed in the second oil sump; asecond reserve tank; and a second siphon allowing flow in bothdirections between the second oil sump and the second reserve tank.

The axle driving apparatus may also include a first detachable oilfilter associated with the first housing and a second detachable oilfilter associated with the second housing.

The axle driving apparatus may also include a first removable lid foraccessing the first detachable oil filter and a second removable lid foraccessing the second detachable oil filter.

Further, the first detachable oil filter may be positioned on a bottomsurface of a first housing and the second detachable oil filter may bepositioned on a bottom surface of a second housing.

Alternatively, the first detachable oil filter may be positioned on arear side of a first housing and the second detachable oil filter may bepositioned on a rear side of a second housing.

Further, the first hydraulic pump may be mounted within the firsthousing a first preselected distance from the first axle and the firsthydraulic motor may be mounted within the first housing a secondpreselected distance from the first axle, the second preselecteddistance being greater than the first preselected distance. In addition,the second hydraulic pump may be mounted within the second housing athird preselected distance from the second axle and the second hydraulicmotor may be mounted within the second housing a fourth preselecteddistance from the second axle, the fourth preselected distance beinggreater than the third preselected distance.

The axle driving apparatus may also include a first rotary bypass valveassembly disposed in the first housing, the first rotary bypass valveassembly including a first rotary shaft having a first end extendingfrom the housing and at least two oil holes and including a first bypassarm connected to the first end of the first rotary shaft for rotatingthe first rotary shaft to connect and disconnect the at least two oilholes with oil drain ports connected to the first hydraulic motor. Theaxle driving apparatus may also include a second rotary bypass valveassembly disposed in the second housing, the second rotary bypass valveassembly including a second rotary shaft having a first end extendingfrom the second housing and at least two oil holes and including asecond bypass arm connected to the first end of the second rotary shaftfor rotating the second rotary shaft to connect and disconnect the atleast two oil holes with oil drain ports connected to the secondhydraulic motor.

Further, the first hydraulic stepless speed change assembly may includea first counter shaft with a first braking mechanism and the secondhydraulic stepless speed change assembly may include a second countershaft with a second braking mechanism.

Further still, the first hydraulic stepless speed change assembly mayfurther include a third counter shaft and the second hydraulic steplessspeed change assembly may further include a fourth counter shaft.

The axle driving apparatus may also include a first magnet located inthe first housing; a second magnet located in the first housing; a thirdmagnet located in the first housing; a fourth magnet located in thesecond housing; a fifth magnet located in the second housing; and asixth magnet located in the second housing.

Further, the first housing may have a first chamber, a second chamberand an opening between the first chamber and the second chamber; thefirst magnet is located in the first chamber; the second magnet islocated in the second chamber; and the third magnet is located in theopening between the first chamber and the second chamber. In addition,the second housing may have a third chamber, a fourth chamber and anopening between the third chamber and the fourth chamber; the fourthmagnet is located in the third chamber; the fifth magnet is located inthe fourth chamber; and the sixth magnet is located in the openingbetween the third chamber and the fourth chamber.

The axle driving apparatus may also include a first check valve locatedin the first speed change assembly; a second check valve located in thefirst speed change assembly; a third check valve located in the firstspeed change assembly; a fourth check valve located in the second speedchange assembly; a fifth check valve located in the second speed changeassembly; and a sixth check valve located in the second speed changeassembly.

Further, the first check valve may be located in a first oil passage inthe first hydraulic pump, the second check valve may be located in asecond oil passage in the first hydraulic pump, the fourth check valvemay be located in a third oil passage in the second hydraulic pump, andthe fifth check valve may be located in a fourth oil passage in thesecond hydraulic pump.

Further still, the axle driving apparatus may include a first chargepump with a first oil groove, wherein the third check valve is locatedin the first oil groove and a second charge pump with a second oilgroove, wherein the sixth check valve is located in the second oilgroove.

Further, the connecting means may be a bar and/or a plate.

Also disclosed herein is an axle driving apparatus of a secondembodiment that includes a housing; a single axle, having a longitudinalaxis, rotatably mounted in the housing; and a hydraulic stepless speedchange assembly disposed within the housing, the speed change assemblyincluding a hydraulic pump having an input shaft projecting from thehousing, the input shaft having a rotational axis substantiallyperpendicular to the single axle, and including a hydraulic motor havingan output shaft drivingly connected to the single axle. The hydraulicpump is mounted within the housing a first preselected distance from thesingle axle and the hydraulic motor is mounted within the housing asecond preselected distance from the single axle, the second preselecteddistance being greater than the first preselected distance.

Also disclosed herein is an axle driving apparatus of a third embodimentthat includes a housing; a single axle, having a longitudinal axis,rotatably mounted in the housing; a hydraulic stepless speed changeassembly disposed within the housing, the speed change assemblyincluding a hydraulic pump having an input shaft projecting from thehousing, the input shaft having a rotational axis substantiallyperpendicular to the single axis, and including a hydraulic motor havingan output shaft drivingly connected to the single axle; and a rotarybypass valve assembly disposed in the housing. The rotary bypass valveassembly includes a rotary shaft having a first end extending from thehousing and at least two oil holes and includes a bypass arm connectedto the first end of the rotary shaft for rotating the rotary shaft toconnect and disconnect the at least two oil holes with oil drain portsconnected to the hydraulic motor.

Also disclosed herein is an axle driving apparatus of a fourthembodiment that includes a housing; a single axle, having a longitudinalaxis, rotatably mounted in the housing; and a hydraulic stepless speedchange assembly disposed within the housing. The speed change assemblyincludes a hydraulic pump having an input shaft projecting from thehousing, the input shaft having a rotational axis substantiallyperpendicular to the single axis; a hydraulic motor having an outputshaft drivingly connected to the single axle; and a first counter shaftwith a braking mechanism.

Further, the hydraulic stepless speed change assembly may include asecond counter shaft.

Further, the braking mechanism may include a fixed friction pad; amovable friction pad having a cam projection; a brake rotor surroundinga gear attached to the first counter shaft and located between the fixedfriction pad and the movable friction pad; a rotary brake shaft having afirst end having a groove and engaged with the movable friction pad; anda brake arm connected to a second end of a rotary brake shaft forrotating the rotary brake shaft to move the movable friction pad closerto the fixed friction pad and press the brake rotor therebetween.

Also disclosed herein is an axle driving apparatus of a fifth embodimentthat includes a housing; a single axle, having a longitudinal axis,rotatably mounted in the housing; a hydraulic stepless speed changeassembly disposed within the housing, the speed change assemblyincluding a hydraulic pump having an input shaft projecting from thehousing, the input shaft having a rotational axis substantiallyperpendicular to the single axis, and including a hydraulic motor havingan output shaft drivingly connected to the single axle; a first magnet;a second magnet; and a third magnet.

Further, the housing may have a first chamber, a second chamber and anopening between the first chamber and the second chamber; the firstmagnet located may be in the first chamber; the second magnet may belocated in the second chamber; and the third magnet may be located inthe opening between the first chamber and the second chamber.

Also disclosed herein is an axle driving apparatus of a sixth embodimentthat includes a housing; a single axle, having a longitudinal axis,rotatably mounted in the housing; a hydraulic stepless speed changeassembly disposed within the housing, the speed change assemblyincluding a hydraulic pump having an input shaft projecting from thehousing, the input shaft having a rotational axis substantiallyperpendicular to the single axis, and including a hydraulic motor havingan output shaft drivingly connected to the single axle; a first checkvalve; a second check valve; and a third check valve.

Further, the first check valve may be located in a first oil passage inthe hydraulic pump and the second check valve may be located in a secondoil passage in the hydraulic pump.

Still further, the axle driving apparatus may include a charge pump withan oil groove, wherein the third check valve may be located in the oilgroove.

Also disclosed herein is an axle driving apparatus of a seventhembodiment that includes a housing; a single axle, having a longitudinalaxis, rotatably mounted in the housing; a hydraulic stepless speedchange assembly disposed within the housing, the speed change assemblyincluding a hydraulic pump having an input shaft projecting from thehousing, the input shaft having a rotational axis substantiallyperpendicular to the single axis, and including a hydraulic motor havingan output shaft drivingly connected to the single axle; and an inputpulley disposed on the input shaft.

Further, the axle driving apparatus may include a spline collarsurrounding the input shaft and a bearing support surrounding the splinecollar, wherein the input pulley is disposed on the bearing support.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The above mentioned features of the invention will be more clearlyunderstood from the following detailed description of the invention readtogether with the drawings in which:

FIG. 1 illustrates a side view, partly in cross-section, of an exemplaryworking vehicle, such vehicle being an example of one type of vehicle onwhich an axle driving apparatus disclosed herein can be utilized.

FIG. 2 illustrates a front view of the vehicle.

FIG. 3 illustrates a plan view of the vehicle showing the transaxleassembly.

FIG. 4 illustrates a first embodiment of a hydraulic circuit diagram fora transaxle assembly.

FIG. 5 illustrates a plan view, partially in cross-section, of a lefttransaxle.

FIG. 6 illustrates a cross-sectional view taken along line VI-VI in FIG.5 of the left transaxle.

FIG. 7 illustrates a cross-sectional view taken along line VII-VII inFIG. 5 of the left transaxle.

FIG. 8 illustrates a cross-sectional view taken along line VIII-VIII inFIG. 5 of the left transaxle.

FIG. 9 illustrates a cross-sectional view taken along line IX-IX in FIG.5 of the left transaxle.

FIG. 10 illustrates a cross-sectional view taken along line X-X in FIG.5 of the left transaxle.

FIG. 11 illustrates a cross-sectional view taken along line XI-XI inFIG. 6 of the left transaxle.

FIG. 12 illustrates a cross-sectional view taken along line XII-XII inFIG. 6 of the left transaxle.

FIG. 13 illustrates a cross-sectional view taken along line XIII-XIII inFIG. 5 of the left transaxle.

FIG. 14 illustrates a top view of the center section.

FIG. 15 illustrates a bottom view of the center section.

FIG. 16 illustrates a left side view of the center section in partialcross-section.

FIG. 17 illustrates a cross-sectional view taken along line XVII-XVII inFIG. 14 of the center section.

FIG. 18 illustrates a cross-sectional view taken along line XVIII-XVIIIin FIG. 16 of the center section.

FIG. 19 illustrates a cross-sectional view taken along line XIX-XIX inFIG. 16 of the center section.

FIG. 20 illustrates a cross-sectional view taken along line XX-XX inFIG. 14 of the center section.

FIG. 21 illustrates a front view of a speed control arm and a bypassarm.

FIG. 22 illustrates a cross-sectional view taken along line XXII-XXII inFIG. 21 of the speed control arm and the bypass arm.

FIG. 23 illustrates a cross-sectional view taken along line XXIII-XXIIIin FIG. 22 of the speed control arm and the bypass arm.

FIG. 24 illustrates a side view of a first embodiment of a pulley andcooling fan attached to a pump shaft.

FIG. 25 illustrates a side view of a second embodiment of a pulley andcooling fan attached to a pump shaft.

FIG. 26 illustrates a second embodiment of a hydraulic circuit diagramfor a transaxle assembly.

FIG. 27 illustrates a third embodiment of a hydraulic circuit diagramfor a transaxle assembly, with a right transaxle and a left transaxlehaving a different hydraulic circuit.

FIG. 28 illustrates a cross-sectional view of a transaxle illustrating acommon housing material and a filter removable from a lower housingpart.

DETAILED DESCRIPTION OF THE INVENTION

The axle driving apparatus disclosed herein is designed to drive avehicle. An exemplary vehicle is shown generally at 1 in FIGS. 1-6.Vehicle 1 is a zero turn radius (ZTR) riding lawn mower. Vehicle 1includes a body frame 3 movably supported by oppositely disposed drivewheels 10L and 10R. A pair of caster wheels 19L and 19R are secured to aforward portion of body frame 3. Vehicle 1 also has an operator's seat16, driving and steering control handles 17L and 17R, and a brake pedal18.

Drive wheels 10L and 10R are rotatably driven by a prime mover, such asengine 2, mounted on body frame 3. Drive wheels 10L and 10R are carriedon left and right axle shafts 9L and 9R, respectively, each of whichhave a wheel mounting flange 9 a. Axle shafts 9L and 9R extend from leftand right transaxles 8L and 8R, respectively, each of which have ahousing 20. Each housing 20, has an upper housing part 21 with framemounting bosses 22 extending therefrom to attach transaxles 8L and 8R toa mounting stay 3 a, which extends downward from body frame 3. A singleaxle shaft 9L(9R) is placed in each housing 20 defining a longitudinalaxis and having a proximal end rotatably mounted in housing 20 and adistal end extending outwardly from a outside wall of housing 20. Eachhousing 20, also has axle support projections 33U and 33L, as shown inFIG. 7, which help to maintain the location of proximal end of axleshaft 9L(9R). The distal end of axle shaft 9L(9R) extends through atubular portion formed in upper housing part 21 and is supported by abearing fitted inside said upper housing 21, then extends outward fromhousing 20.

A shaft 2 a extends downward from engine 2 to drive an output pulley 4,a PTO (power take-off) electric clutch 12, and an output pulley 11. Abelt 5 fits around output pulley 4 and input pulleys 6L and 6R, whichare located on transaxles 8L and 8R, below cooling fans 7L and 7R,respectively. A belt 13 fits around output pulley 13 and an input pulley14 that is connected to a shaft 15 a extending from a mower 15positioned beneath body frame 3.

FIG. 3 illustrates a plan view of a transaxle assembly includingtransaxles 8L and 8R. Housings 20 of transaxles 8L and 8R are separateand distinct from one another and do not have a shared common housing.Facing side surfaces of upper housing parts 21 of transaxles 8L and 8Rare connected together with a connecting bar 137 that extends fromopenings 24, as shown in FIG. 10, in upper housing parts 21 oftransaxles 8L and 8R to span a space between transaxles 8L and 8R. Endsof connecting bar 137 may be pressure fitted or friction fitted intoopenings 24, which are coaxial to axles 9L and 9R. A pair of hollowtubes 138 are rotatably mounted on connecting bar 137 allowing forcontact with belt 13 when mower 15 is lifted up. In addition, uppersurfaces of upper housing parts 21 of transaxles 8L and 8R are alsoconnected together via a connecting plate 139 that is bolted to theupper surfaces of upper housing parts 21. Although both are shown, theconnecting means between transaxles 8L and 8R may be connecting bar 137alone, connecting plate 139 alone, or both connecting bar 137 andconnecting plate 139. Connecting transaxles 8L and 8R in this fashionleaves a space therebetween that allows for the passage of belt 13 inthe space between transaxles 8L and 8R giving the advantage of a greaterground clearance of output pulley 11.

As mentioned above, housings 20 of transaxles 8L and 8R are separate anddistinct from one another. Housings 20 are not mirror images of oneanother and have distinguishing features. For example, cooling fins orribs 23L and 23R, which extend from an upper surface of upper housingparts 21, may have different configurations and/or profiles from oneanother. For instance, as shown in FIG. 3 cooling fins or ribs 23L maybe bent at a different angle than cooling fins or ribs 23R. Theconfiguration and profile of cooling fins or ribs 23L and 23R optimizesand improves air flow for cooling oil within transaxles 8L and 8R.Cooling fans 7L and 7R rotate together with input pulleys 6L and 6R inthe same direction. Cooling fins or ribs 23L and 23R are formed alongthe direction of cooling air flow for improved cooling efficiency sothat the overall profile of right and left transaxles 8L and 8R areasymmetrical.

Transaxles 8L and 8R have the same components and while left transaxle8L will be described with reference to FIGS. 5-26, right transaxle 8Rhas the same components. Transaxle 8L has a housing 20 that includes anupper housing part 21 and a lower housing part 26 joined together withbolts 27. Housing 20 has a hydraulic stepless speed change assemblydisposed therein. The hydraulic stepless speed change assembly includesa hydraulic variable displacement axial piston pump 50 and a hydraulicfixed displacement axial piston motor 60. A center section 67 is mountedin an enlarged region of housing 40 and has a pump mounting surface 70for mounting pump 50 thereon and has a motor mounting surface 73 formounting motor 60 thereon. Center section 67 is attached to upperhousing part 21 through a plurality of bolts 68, each of which passthrough a hollow dowel pin 69. Dowel pin 69 allows for the correctpositioning of center section 67 at a predetermined position. Housing 20has a first chamber 31 housing a gear train, a second chamber 34 servingas an oil sump, and a third chamber 39, as shown in FIG. 13.

Pump 50 is mounted within housing 20 a first preselected distance fromaxle 9L and motor 60 is mounted within housing 20 a second preselecteddistance from axle 9L. The second preselected distance is greater thanthe firs preselected distance. This may be achieved by having centersection 67 be d-shaped such that pump 50 is located between axle 9L andmotor 60. The rotational axis of pump 50 located on center section 67 isperpendicular to the rotational axis of axle shaft 9L and the rotationalaxis of motor 60 located on center section 67 is parallel to therotational axis of axle shaft 9L in the second chamber 34. Thisarrangement brings the pump shaft 51 close to engine 2, therebydecreasing the amount of space need to mount transaxle 8L. Thearrangement also locates pump shaft 51 substantially in the middle ofthe housing 20 so that cooling fan 7L located at an external distal endof pump shaft 51 can cover substantially the entirety of housing 20 andthereby efficiently circulate cooling air.

As best seen in FIG. 5, one end of motor 60 is mounted on to motormounting surface 73 of center section 67 via a valve plate 63 having apair of openings for communication with kidney ports 74 a and 74 b.Motor 60 includes a cylinder block 62 which is rotatably disposed onvalve plate 63. A plurality of pistons are fitted for reciprocatingmovement into a plurality of cylinder bores defined in cylinder block62. The other end of motor 60 has a fixed swash plate 64. The heads ofthe pistons abut a thrust bearing of the fixed swash plate 64. A motoroutput shaft 61 extends longitudinally through cylinder block 62parallel to axle shaft 9L. One end of motor shaft 61 extends through anopening in valve plate 63 and the other end extends through an openingin fixed swash plate 64.

A first counter shaft 119 extends longitudinally parallel to andadjacent to motor shaft 61. A second counter shaft 122 extendslongitudinally parallel to and is located between first counter shaft119 and axle shaft 9L. An output gear 118 is provided on motor shaft 61,which engages with a first reduction gear 120 mounted on first countershaft 119, which in turn engages with a second reduction gear 123mounted a pinion gear 124 mounted on second counter shaft 122. Secondreduction gear 123 then in turn engages with a bull gear 125 mounted onaxle shaft 9L. This gear train transmits the driving force from motorshaft 61 to axle shaft 9L in the first chamber 31.

A braking mechanism is shown in FIGS. 9 and 21-23. A brake rotor 121engages first reduction gear 120 mounted on first counter shaft 119.Brake rotor 121 rotates with motor shaft 61 between a fixed friction pad128 and a movable friction pad 130. Fixed friction pad 128 is fitted toupper housing part 21. Movable friction pad 130 is integrally formed atthe base of a rotary brake shaft 129 and the movable friction pad 130has a cam projection 131 projecting from a surface not facing brakerotor. A sleeve 132 is fixed to upper housing part 21 and has an openingthat rotary brake shaft 129 extends through. A V-shaped groove 133 isformed at the end of rotary brake shaft 129 where sleeve 132 is locatedand engages with cam projection 131. The other end of rotary brake shaft129 not adjacent movable friction pad 130 has a brake arm 29 mountedthereon that extends perpendicular to rotary brake shaft 129 and areturn spring 134 surrounding rotary brake shaft 129 such that brake arm29 is located between return spring 134 and sleeve 132.

When brake pedal 18 is depressed, brake arm 29 is actuated to rotaterotary brake shaft 129, movement of cam projection 131 presses V-shapedgroove 133 causing movable friction pad 130 to move towards fixedfriction pad 128. This movement causes brake rotor 121 to be clampedbetween movable friction pad 130 and fixed friction pad 128, stoppingmovement of brake rotor 121 and in turn first counter shaft 120, therebyresulting in a braking of the gear train. Return spring 134 facilitatesquick release of the braking action and movement of spring 134 islimited by limiter pin 135. The illustrated braking mechanism is merelyillustrative of one suitable braking mechanism and other suitablebraking mechanisms can be utilized if desired.

As best seen in FIG. 6, one end of pump 50 is mounted on pump mountingsurface 70 of center section 67 via a valve plate 53 that has a pair ofopenings for communication with kidney ports 71 a and 71 b. Pump 50includes a cylinder block 52 rotatably disposed on valve plate 53.Pistons are fitted into a plurality of cylindrical bores of cylinderblock 52. The other end of pump 50 has a movable swash plate 54, whichmay be a cradle-type swash plate. Above movable swash plate 54 is anarcuate guide 25 for movable swash plate 54. Movable swash plate 54 isprovided for selectively varying the displacement of hydraulic pump 50.A pump input shaft 51 extends longitudinally through cylinder block 52and is perpendicular to axle shaft 9L. It will be recognized by thoseskilled in the art that rotation of pump shaft 51 serves to drivehydraulic pump 52. Pump shaft 51 engages with a spline bore provided onthe rotational axis of cylinder block 52 such that cylinder block 52rotates with pump shaft 51.

As best seen in FIGS. 8 and 21, a connecting arm 55 is attached tomovable swash plate 54 at a first end and extends downward therefrom. Afirst end of a control shaft 58 extends from a second end of connectingarm 55 and a second end of control shaft 58 has a speed control arm 28disposed thereon. Speed control arm 28 has a slot 56 through which astopper 57 goes through and attaches to housing 21. Speed control arm 28is mechanically connected to control lever 17L with one or more rodlinks or wire cables, such that when control lever 17L is moved forwardor backward, speed control arm 28 moves forward or backward. Movement ofspeed control arm 28 is translated through control shaft 58 toconnecting arm 55 and then to movable swash plate 54. Movement of swashplate 54 changes the direction cylinder block 52 rotates and therebyswitches the transaxle assembly between forward movement, neutral, andreverse movement. When stopper 57 contacts the end of slot 56, it limitsthe movement of speed control arm 28.

As best seen in FIG. 24, one end of pump shaft 51 extends from upperhousing 21 and through a stop ring 146 and then a spline collar 142,both of which surround pump shaft 51. A bearing support part 143 thatmay be cup shaped surrounds spline collar 142 and extends downward tocover the opening in upper housing 21 through which pump shaft 51extends. Bearing support part 143 is separated from upper housingthrough a bearing 145 having a seal. Input pulley 6L is disposed on anoutside of bearing support part 143 such that a rotary part 144 of inputpulley 6L faces bearing support part 143. This configuration ofdisposing input pulley 6L accommodates for the low positioning of engine2. It is noted that this configuration may also be utilized in an axledriving apparatus other than for driving zero turn radius vehicles.

FIG. 24 illustrates a first embodiment for disposing cooling fan 7Lhaving fan blades 148 and a main body 149 about pump shaft 51. Main body149 of cooling fan 7L is disposed about spline collar 142 and isattached to bearing support part 143 through bolts 150. In this firstembodiment the end of pump shaft 51 extending through spline collar 142has a nut 147 applied thereto. The rotation of pump shaft 51 rotatesspline collar 142, bearing support part 143 with an outer ring ofbearing 145, input pulley 6L, and cooling fan 7L.

FIG. 25 illustrates a second embodiment for disposing cooling fan 7Lhaving fan blades 148 and a main body 149 about pump shaft 51. Splinecollar 142 rests on a first stop ring 154 and a wave washer 153surrounding pump shaft 51 rests on top of spline collar 142. A splinehub 152 surrounds pump shaft 51 and is disposed on top of wave washer153. A main body 149 of cooling fan 7L interlocks with spline hub 152and a portion also rests on wave washer 153. Wave washer 153 may be aflexible metal and has the advantage of reducing noise between coolingfan 7L and input pulley 6L. A spacer 156 surrounds pump shaft 51 and isdisposed on top of spline hub 152 and a second stop ring 155 surroundspump shaft 51 and is disposed on top of spacer 156. The rotation of pumpshaft 51 rotates spline collar 142, bearing support part 143, and inputpulley 6L and also rotates spline hub 152 and cooling fan 7L.

The hydraulic circuit for fluid flow between pump 50 and motor 60 willbe described with reference to FIGS. 4 and 14-20. Pump mounting surface70 on center section 67 has a pair of kidney-shaped ports 71 a and 71 bto take in or discharge oil in cylinder block 52 of pump 50 and a leakoil drain groove 72. Motor mounting surface 73 on center section 67 hasa pair of kidney-shaped ports 74 a and 74 b to take in or discharge oilin cylinder block 62 of motor 60 and a leak oil drain groove 75. Inorder to establish fluid communication between port 71 a and port 74 a atilt oil passage 77 a is provided in center section 67 that connectsport 71 a to a first oil passage 76 in center section 67. Port 74 a isalso connected to first oil passage 76. Tilt oil passage 77 a has an endthat opens to the surface of center section 67 but is provided with alid 77 b to close the end. In order to establish fluid communicationbetween port 71 b and 74 b a second oil passage 78 is provided in centersection 67, which connects ports 71 b and 74 b. First oil passage 76 hasa first charge check valve 79 a and second oil passage 78 has a secondcharge check valve 79 b. Stopper ribs 81U and 81L are disposed withinhousing 20 adjacent charge check valves 79 b and 79 a, respectively, asshown in FIGS. 6, 10, and 11. The end surfaces of the charge checkvalves 79 b and 79 a contact each stopper ribs 81U and 81L so thatcharge check valves 79 b and 79 a never fall out from center section 67.Accordingly, a closed hydraulic circuit is defined to circulate theoperating oil between hydraulic pump 50 and hydraulic motor 60.

Operation of pump 50 causes one of first oil passage 76 or second oilpassage 78 to be under high pressure. When first oil passage 76 is underhigh pressure first charge check valve 79 a is also under high pressureand its outlet is closed by its ball valve. Similarly, when second oilpassage 78 is under high pressure second charge check valve 79 b is alsounder high pressure and its outlet is closed by its ball valve. When oneof first and second charge check valves 79 a or 79 b is under highpressure the other of first and second charge check valves 79 a or 79 bis under low pressure and the inlet and outlet are connected andreplenished with oil. Second charge check valve 79 b, located in secondoil passage 78, is under high pressure when vehicle 1 is traveling inreverse. Second charge check valve 79 b has an orifice 80 that bypassesthe inlet and outlet and thereby broadens the area of the neutral bandof pump 50.

As best seen in FIG. 9, one end of each of first oil passage 76 andsecond oil passage 78 lead to drain ports 85 a and 85 b, respectively.Drain ports 85 a and 85 b run parallel to each other and are connectedvia a shaft hole 86 that runs perpendicular to and intersects both drainports 85 a and 85 b. A rotary bypass valve including a rotary bypassshaft 87 is disposed within shaft hole 86. Rotary bypass shaft has oilholes 88 a and 88 b, which are positioned to align with drain ports 85 aand 85 b, respectively. Rotary bypass shaft 87 extends from centersection 67 and from upper housing 21 and has a bypass arm 30 attached toits end.

The rotary bypass valve is switchably operated between a shutoffposition and a communication position by rotating rotary bypass shaft 87ninety degrees with bypass arm 30 about the axis of rotary bypass shaft87. In the shutoff position, oil holes 88 a and 88 b are not incommunication with drain ports 85 a and 85 b. In the communicationposition oil holes 88 a and 88 b are in communication with drain ports85 a and 85 b. Therefore when the transaxle 8L is in traction, it iseasy to keep the axle shaft 9L free-wheeling by operating bypass arm 30.

Center section 67 also has a charge pump case mounting surface 82opposite to pump mounting surface 70 for mounting a hydraulic PTO unithaving a charge pump 90. Charge pump case mounting surface 82 has acharge port 83 that leads to a passage connected to an inlet of firstand second charge check valves 79 a and 79 b and an oil groove 84.

Charge pump 90, as shown in FIGS. 6, 8, 11, and 12 is a pump which iscontained in a charge pump casing 91 attached to charge pump casemounting surface 82 of center section 67 through bolts 92. Pump shaft 51extends through charge pump casing 92 and drives charge pump 90. Chargepump 90 is in fluid communication with first and second oil passages 76and 78 through first and second charge check valves 79 a and 79 b andcharge port 83.

Charge pump 90 has an inner rotor 93 disposed about pump shaft 51 andhas a joint pin 94 that extends through an opening in pump shaft 51 andis attached at its ends to inner rotor 93. An outer rotor 95 is disposedabout inner rotor 93. Oil groove 84 in center section 67 is aligned withan oil groove 98 in charge pump casing 91. Oil groove 98 has an oil hole99 that leads to an inlet auxiliary port 107. Oil groove 98 also has anoil hole 101 that drains oil when an implement relief valve 100 adjuststhe pressure of discharge port 97. Discharge port 97 of charge pump 90is in communication with outlet auxiliary port 106. Oil groove 98 alsohas an oil hole 103. The oil flowing over oil groove 98 goes through oilhole 103 to charge relief valve 102. The oil discharged from chargerelief valve 102 goes through drain hole 104 then flows down to an oilsump 34 at the bottom of charge pump casing 91. Charge pump 90 also hasa suction port 96 that leads to oil sump 34. Oil groove 98 also has asuction valve 105 that is in communication with suction port 96. Suctionvalve 105 may act as a third check valve that prevents free-wheelingwhen vehicle 1 stops and comes to a halt.

As shown in FIG. 4, both transaxle 8L and 8R have charge pumps 90 withauxiliary ports 106 and 107. In transaxle 8L the auxiliary ports areopen and connected to a hydraulic actuator 108 and in transaxle 8R theauxiliary ports are open and connected to a hydraulic actuator 109.Alternatively, transaxle 8R may have auxiliary ports that are closed offvia a bypass conduit 158, as shown in FIG. 26 or transaxle 8R may nothave auxiliary ports at all, as shown in FIG. 27. Transaxle 8R shown inFIGS. 26 is the same as transaxle 8L except for the presence of bypassconduit 58 and absence of a hydraulic actuator and transaxle 8R shown inFIG. 27 is the same as transaxle 8L except for the absence of auxiliaryports 106, 107 and a hydraulic actuator. Hydraulic actuator 108 for useas hydraulic equipment adjunct to working vehicle such as lift apparatusfor mower.

Charge pump 90 serves to draw lubricating oil in oil sump 34 into chargepump 90 and ultimately into first and second oil passages 76 and 78through first and second charge check valves 79 a and 79 b. As shown inFIG. 6, a detachable oil filter 36 is inserted into rear side opening 37in housing 20. Once oil filter 36 is inserted into opening 37, opening37 is sealed with lid 38. Oil filer 36 is in communication with suctionvalve 105 and suction port 96 of charge pump 90.

Alternatively, as shown in FIG. 28, a detachable annular oil filter 162is inserted in a bottom side opening 164 of housing 20. Once oil filter162 is inserted into opening 164, opening 164 is sealed with lid 165.Charge pump case 161 is attached to center section 159 with a slidingguide pin 160. A spring 163 located between floating charge pump casing161 and lid 165 and flexibly supports charge pump case 161 so it isfloating within oil filter 162 on spring 163. Charge pump case 161 andspring 163 have a similar function as the charge relief valve 102 as setforth above.

Housing 20 has an oil sump 34 located therein and the hydraulic steplessspeed change assembly is at least partially immersed in oil sump 34. Oilsump 34 is filled with oil for lubricating and operating the HST. Asbest seen in FIG. 7, reserve oil tank 111 may be disposed in a holder116, which is attached to an outside surface of upper housing 21.Reserve tank 111 is filled with oil having a normal level 113 and has acap 114 having a breather that communicates the interior of reserve tank111 with the atmosphere. A fine tube or siphon 112 extends from aconnector 115 into the oil in reserve tank 111. Connector 115 isattached to reserve tank 111 and is in communication with oil sump 34through a vertical oil bore formed in upper housing 21. Siphon 112allows for oil to flow between sump 34 and reserve tank 111.

As the volume of oil in oil sump 34 increases as the temperature of theoil increases during operation of the HST, the increased volume of oilis directed into reserve tank 111 through connector 115 and siphon 112.In addition, as the volume of oil in oil sump 34 decreases as thetemperature of the oil decreases, the oil returns to oil sump 34 fromreserve tank 111 through siphon 112 and connector 115.

As discussed above, housing 20 has a first chamber 31 housing a geartrain, a second chamber 34 serving as an oil sump, and a third chamber39, which is an opening located between first chamber 31 and secondchamber 34. As best seen in FIGS. 5 and 13, the housing 20 utilizes amagnetic oil-cleaning assembly for cleaning the oil therein by removingmetal shavings, generated through the chafing of the gears. Firstchamber 31 has a first magnet 32 preferably located near bull gear 125.Second chamber 34 has a second magnet 35 preferably located near oilfilter 36. Third chamber 39 has a communicating bore 43 to first chamber31 and a communicating bore 44 to second chamber 34 and a lid 41. Oilpasses between first chamber 31 and second chamber 34 through thirdchamber 39. Third chamber 39 is an opening between first chamber 31 andsecond chamber 34 and has a third magnet 40 that sits in a seat plate42.

The axle driving apparatus disclosed above is advantageous for use in azero turn radius vehicle, but is not limited to such. It allows a lawnor garden tractor, or other vehicle, with the axle driving apparatusdisposed therein to make zero radius turns and facilitates mowing closeto trees or other obstacles.

While preferred embodiments have been shown and described, it will beunderstood that there is no intent to limit the invention to suchdisclosure, but rather it is intended to cover all modifications andalternate constructions falling within the spirit and scope of theinvention as defined in the appended claims.

1. An axle driving apparatus for a vehicle, comprising: a first housinghaving a first plurality of cooling fins; a first axle, having a firstlongitudinal axis, rotatably mounted in the first housing; a firsthydraulic stepless speed change assembly disposed within the firsthousing, the first hydraulic stepless speed change assembly including afirst hydraulic pump having a first input shaft, said first input shafthaving a rotational axis substantially perpendicular to said first axle,and including a first hydraulic motor having a first output shaftdrivingly connected to said first axle; a second housing having a secondplurality of cooling fins; a second axle, having a second longitudinalaxis, rotatably mounted in the second housing; a second hydraulicstepless speed change assembly disposed within the second housing, thesecond hydraulic stepless speed change assembly including a secondhydraulic pump having a second input shaft, said second input shafthaving a rotational axis substantially perpendicular to said secondaxle, and including a second hydraulic motor having a second outputshaft drivingly connected to said second axle; and a connecting meansconnecting the first and second housings; wherein the first plurality ofcooling fins and the second plurality of cooling fins have differentconfigurations.
 2. The axle driving apparatus of claim 1, wherein thefirst plurality of cooling fins are bent at an angle different from anangle at which the second plurality of cooling fins are bent.
 3. Theaxle driving apparatus of claim 1, further comprising: a first hydraulicPTO unit having a first charge pump, wherein the first hydraulic PTOunit is connected to a first plurality of auxiliary ports in the firsthousing.
 4. The axle driving apparatus of claim 3, wherein the secondhousing has a second plurality of auxiliary ports.
 5. The axle drivingapparatus of claim 4, further comprising a second hydraulic PTO unithaving a second charge pump, wherein the second hydraulic PTO unit isconnected to the second plurality of auxiliary ports.
 6. The axledriving apparatus of claim 4, wherein the second plurality of auxiliaryports are closed off.
 7. The axle driving apparatus of claim 1, furthercomprising: a first input pulley disposed on the first input shaft; anda second input pulley disposed on the second input shaft.
 8. The axledriving apparatus of claim 7, further comprising: a first spline collarsurrounding the first input shaft; a first bearing support surroundingthe first spline collar; a second spline collar surrounding the secondinput shaft; and a second bearing support surrounding the second splinecollar; wherein the first input pulley is disposed on the first bearingsupport and the second input pulley is disposed on the second bearingsupport.
 9. The axle driving apparatus of claim 1, further comprising: afirst input pulley; a first cooling fan mounted on the first inputshaft; a first wave washer located between the first input pulley andthe first cooling fan; a second input pulley; a second cooling fanmounted on the second input shaft; and a second wave washer locatedbetween the second input pulley and the second cooling fan.
 10. The axledriving apparatus of claim 1, further comprising: a first oil sumpformed in the first housing, wherein the first hydraulic stepless speedchange assembly is at least partially immersed in the first oil sump; afirst reserve tank; a first siphon allowing flow in both directionsbetween the first oil sump and the first reserve tank; a second oil sumpformed in the second housing, wherein the second hydraulic steplessspeed change assembly is at least partially immersed in the second oilsump; a second reserve tank; and a second siphon allowing flow in bothdirections between the second oil sump and the second reserve tank. 11.The axle driving apparatus of claim 1, further comprising: a firstdetachable oil filter associated with the first housing; and a seconddetachable oil filter associated with the second housing.
 12. The axledriving apparatus of claim 11, further comprising: a first removable lidfor accessing the first detachable oil filter; and a second removablelid for accessing the second detachable oil filter.
 13. The axle drivingapparatus of claim 11 wherein the first detachable oil filter ispositioned on a bottom surface of a first housing and the seconddetachable oil filter is positioned on a bottom surface of a secondhousing.
 14. The axle driving apparatus of claim 11 wherein the firstdetachable oil filter is positioned on a rear side of a first housingand the second detachable oil filter is positioned on a rear side of asecond housing.
 15. The axle driving apparatus of claim 1 wherein: thefirst hydraulic pump is mounted within the first housing a firstpreselected distance from the first axle and the first hydraulic motoris mounted within the first housing a second preselected distance fromthe first axle, the second preselected distance being greater than thefirst preselected distance; and the second hydraulic pump is mountedwithin the second housing a third preselected distance from the secondaxle and the second hydraulic motor is mounted within the second housinga fourth preselected distance from the second axle, the fourthpreselected distance being greater than the third preselected distance.16. The axle driving apparatus of claim 1, further comprising: a firstrotary bypass valve assembly disposed in the first housing, the firstrotary bypass valve assembly including: a first rotary shaft having afirst end extending from the housing and at least two oil holes; andincluding a first bypass arm connected to the first end of the firstrotary shaft for rotating the first rotary shaft to connect anddisconnect the at least two oil holes with oil drain ports connected tothe first hydraulic motor; and a second rotary bypass valve assemblydisposed in the second housing, the second rotary bypass valve assemblyincluding: a second rotary shaft having a first end extending from thesecond housing and at least two oil holes; and including a second bypassarm connected to the first end of the second rotary shaft for rotatingthe second rotary shaft to connect and disconnect the at least two oilholes with oil drain ports connected to the second hydraulic motor. 17.The axle driving apparatus of claim 1, wherein: the first hydraulicstepless speed change assembly includes a first counter shaft with afirst braking mechanism; and the second hydraulic stepless speed changeassembly includes a second counter shaft with a second brakingmechanism.
 18. The axle driving apparatus of claim 17, wherein: thefirst hydraulic stepless speed change assembly further comprises a thirdcounter shaft; and the second hydraulic stepless speed change assemblyfurther comprises a fourth counter shaft.
 19. The axle driving apparatusof claim 1, further comprising: a first magnet located in the firsthousing; a second magnet located in the first housing; a third magnetlocated in the first housing; a fourth magnet located in the secondhousing; a fifth magnet located in the second housing; and a sixthmagnet located in the second housing.
 20. The axle driving apparatus ofclaim 19, wherein: the first housing has a first chamber, a secondchamber and an opening between the first chamber and the second chamber;the first magnet is located in the first chamber; the second magnet islocated in the second chamber; and the third magnet is located in theopening between the first chamber and the second chamber; the secondhousing has a third chamber, a fourth chamber and an opening between thethird chamber and the fourth chamber; the fourth magnet is located inthe third chamber; the fifth magnet is located in the fourth chamber;and the sixth magnet is located in the opening between the third chamberand the fourth chamber.
 21. The axle driving apparatus of claim 1,further comprising: a first check valve located in the first speedchange assembly; a second check valve located in the first speed changeassembly; a third check valve located in the first speed changeassembly; a fourth check valve located in the second speed changeassembly; a fifth check valve located in the second speed changeassembly; and a sixth check valve located in the second speed changeassembly.
 22. The axle driving apparatus of claim 21, wherein: the firstcheck valve is located in a first oil passage in the first hydraulicpump and the second check valve is located in a second oil passage inthe first hydraulic pump; and the fourth check valve is located in athird oil passage in the second hydraulic pump and the fifth check valveis located in a fourth oil passage in the second hydraulic pump.
 23. Theaxle driving apparatus of claim 22, further comprising: a first chargepump with a first oil groove, wherein the third check valve is locatedin the first oil groove; and a second charge pump with a second oilgroove, wherein the sixth check valve is located in the second oilgroove.
 24. The axle driving apparatus of claim 1, wherein theconnecting means is a bar and/or a plate.
 25. An axle driving apparatusfor a vehicle, comprising: a housing; a single axle, having alongitudinal axis, rotatably mounted in the housing; a hydraulicstepless speed change assembly disposed within the housing, the speedchange assembly including a hydraulic pump having an input shaftprojecting from the housing, the input shaft having a rotational axissubstantially perpendicular to the single axle, and including ahydraulic motor having an output shaft drivingly connected to the singleaxle; an input pulley disposed on the input shaft; a spline collarsurrounding the input shaft; and a bearing support surrounding thespline collar, wherein the input pulley is disposed on the bearingsupport.
 26. The axle driving apparatus of claim 25, further comprising:a cooling fan mounted on the input shaft; and a wave washer locatedbetween the input pulley and the cooling fan.